It is known in the art to apply a heat decomposable material, for example, a heat decomposable organic based material containing metals, to a surface of a heated glass substrate in order to develop an adherent coating of such metals on the surface of the glass substrate. When the heated decomposable material is applied to the heated glass substrate, the heat decomposable portion of the applied material volatilizes leaving behind on the surface of the glass substrate an adherent oxide form of the metals contained therein.
I have discovered that if the metal composition of the metal oxide coating on the surface of the glass substrate falls within certain percentages of cobalt, manganese and copper, the adherent coating will have a very desirable gray color on a clear glass substrate. By a very desirable gray color, I mean that the coated glass substrate will absorb more light than a prior art, grey coated glass product of which I am aware. By absorbing more light, less light is reflected by the gray coated glass substrate. This greater absorption eliminates a yellow reflection that was obtained with the prior art gray coated glass product, thereby providing the more desirable gray color achieved with the coated glass substrate of my invention. The more desirable gray color of my invention may be utilized both as an architectural glass product and as an automotive glass product. The previous metal oxide coating which I am aware of for producing a gray color on a clear glass substrate had a coating chemistry of approximately 95% cobalt and 5% iron for the metals forming the metal oxide coating.
A prior art study was carried out with respect to the subject matter of this specification in the U.S. Patent and Trademark Office. As a result of that search, the following patents were cited: U.S. Pat. Nos. 3,850,665; 3,984,591; 4,120,679; 4,129,434; 4,239,816; 4,259,371; 4,292,347; and 4,344,986. These patents will be discussed individually below.
U.S. Pat. No. 3,850,665 for a "Process for Forming a Metal Oxide Coating on a Substrate and Resulting Products" issued on Nov. 26, 1974. This patent discloses forming a metal oxide coating on a vitreous or nonvitreous substrate by applying to a substrate a composition comprising an acetyl acetonate coprecipitate of two or more metals. The substrate and composition are simultaneously or subsequently heated to convert the coprecipitate on the substrate to leave a metal oxide coating which is at least partly composed of an oxidic compound of two or more metals. While the patent mentions the metals which will be disclosed below, there is no teaching or suggestion in this patent of the compositional ranges which will be disclosed below, and that these ranges will product a gray color which has the desirable attributes already discussed above which are not found in the gray colored glass disclosed above as being in the prior art.
U.S. Pat. No. 3,984,591 for a "Process for Forming a Metallic Oxide Coating" issued on Oct. 5, 1976. This patent discloses a metallic oxide coating being formed on a substrate which may be vitreous, partly vitreous, or nonvitreous. The coating is developed by applying to the substrate a solution of one or more metallic salts selected from the group of acetates, halides and nitrates in aprotic solvent having a dielectric constant greater than 15 and a dipolar moment greater than 3D. The substrate and applied solution are then subjected to heat to convert in situ the metallic salt to form a coating comprising at least one metallic oxide.
U.S. Pat. No. 4,120,679 for a "Production of Semi-Reflecting Glass Products" issued on Oct. 17, 1978. This patent discloses a process of producing semi-reflecting glass products. The process includes the step of applying to at least a portion of one surface of the product a solution of at least one charge-transfer complex in a nonaqueous organic solvent therefor. The product is heated prior to the application to a temperature sufficient to evaporate the solvent and cause pyrolysis of the charge-transfer complex.
U.S. Pat. No. 4,129,434 for a "Process for Forming a Metal Oxide Coating" issued on Dec. 12, 1978. This patent discloses the formulation of a metal oxide coating on a vitreous or nonvitreous substrate by applying a solution containing at least one metal compound to the substrate and then heating the coated substrate to convert the compound in situ to leave a coating of metal acetyl acetonate or mixture of metal acetyl acetonates in a solvent.
U.S. Pat. No. 4,239,816 for "Organic Additives for Organo Metallic Compositions" issued on Dec. 16, 1980. This patent discloses a coating composition for the pyrolytic decomposition of metal oxide films comprising an organo metallic coating reactant, a high boiling point organic compound which modifies the rate of film formation and decreases the particle size of the metal oxide, and, preferably, a nonflammable halocarbon containing solvent.
U.S. Pats. Nos. 3,984,591; 4,120,679; 4,129,434; and 4,239,816 do not teach or suggest the specific materials that will be disclosed to achieve the very desirable gray color on a glass substrate as is achieved if one follows the teachings of my invention.
U.S. Pat. No. 4,259,371 for a "Method for Improving the Alkali Durability of Metal Oxide Films Formed by Pyrolysis" issued on Mar. 31, 1981. This patent discloses a method for improving the uniformity and durability of a pyrolytically deposited metal oxide film on glass by cooling the coating solution and/or the atomizing air prior to the application of the coating composition to the hot glass. While the patent mentions a number of different materials which may be used in the process, there is no specific teaching or suggestion of the use of the three metals I will propose below in the percentages also to be proposed below to achieve a gray color coating on a glass substrate which has the desirable characteristics which I have described above, namely, that of absorbing more light than previously known compositions thereby eliminating a yellow reflection that was obtained with the previously known gray composition.
U.S. Pat. No. 4,292,347 for a "Pyrolytic Coating Reactant for Defect and Durability Control" issued on Sept. 29, 1981. This patent discloses a mixture of carboxylate and diketonate coating reactants which form a metal oxide film with essentially the same reflectance and transmittance as a metal oxide film formed from diketonate coating reactants alone, while providing improvement in control of defects in the film. Once again, while there are a number of metal coating materials mentioned, there is no disclosure or suggestion of the particular metal coating materials and the concentration of these metal coating materials that I will disclose below for obtaining a very desirable gray color on a glass substrate.
U.S. Pat. No. 4,344,986 for a "Method of Delivering Powder Coating Reactants" issued on Aug. 17, 1982. The patent discloses a method for depositing a coating from a turbulant, gaseous stream of a powder coating reactant delivered to a substrate surface through a slot shaped nozzle. The patent does not teach or suggest the particular coating metal oxides and concentrations therein of metals which I will set out below for obtaining a very desirable gray color on a glass substrate.